The present invention relates to an improved split bolt for use in combination with an insert embedded in a concrete slab to provide for the attachment to the slab of a detachable means for lifting the object. Further, it is related to and an improvement over U. S. patent application Ser. No. 427,781, filed Dec. 26, 1973 and entitled "Split Bolt. "
In recent years, there has come into rather wide usage a form of building construction referred to as the tilt-up slab method wherein large concrete slabs are cast on the floor or the building or on a level ground surface, and then lifted to a vertical position and interconnected to form the walls of the building. The means used for lifting the slabs must be removable after the slabs have been lifted into place to present a smooth surface on the walls of the building. Generally, the lifting attachments are installed and removed at the building site. Therefore, they should be easily and rapidly installed and removed in order to save maximum time.
One practice to embed a nut member or insert in the concrete slab and then to attach a lifting eye to the slab by passing a bolt through the eye and threading it into the nut member or insert. While this provides a satisfactory anchoring for the lifting eye, it requires threading the bolt into the insert, which, because of small particles of concrete on the thread surfaces, may require the use of a wrench to thread the bolt into the insert. The result is an increase in the time required to erect the walls. Additional time is expended when a wrench is required to remove the bolt.
U. S. Pat. No. 3,456,547 solves some of the above problems by providing a bolt means which is rapidly inserted in a nut means or insert and requires only a partial revolution to lock the bolt securely in place. The bolt means is formed from a pair of separate longitudinal cylindrical segments such as are formed when a conventional bolt is split along its longitudinal axis into two bolt halves. A portion of the bolt along the longitudinal axis is removed so that when the two segments are placed together, they may be easily inserted into the nut means.
After the two bolt segments are inserted in the nut means, a key member or wedge is positioned between the bolt segments to separate them into engagement with the female threads on the nut means. To remove the bolt, the key is withdrawn and the two segments of the bolt are brought together. This disengaes the threaded surfaces and permits withdrawal of the bolt.
The split bolt disclosed in U. S. Pat. No. 3,456,547 is highly effective, but it has a disadvantage in that the wedge, or "key" as it is referred to in the patent, is not readily removed once the bolt is in use. After the slab is lifted and installed, the wedge must be extracted from between the bolt segments in order to remove the bolt. Tab or ear means are disclosed in U.S. Pat. No. 3,456,547 for gripping and lifting the wedge, but the forces of installing and securing the bolt, as well as lifting and transporting the object, frequently cause the "key" to become tightly gripped or wedged between the bolt portions, and therefore difficult to remove. Further, the key or wedge is relatively thin, as compared to its width, and is easily bent, resulting in further inconvenience by its being rendered unusable or requiring time to straighten it out so that it will slide between the bolt segments.
The split-bolt of U.S. patent application Ser. No. 427,781, is basically similar to that of U.S. Pat. No. 3,456,547 in that it has a similar type wedge. It improves upon the split-bolt of U.S. Pat. No. 3,456,547 because it has a further means to extract the wedge from between the bolt portions as well as a wedge shaped tip to cause the bolt segments to be spaced or wedged apart. But the split-bolt of Ser. No. 427,781 can still suffer from the inconvenience of the wedge member becoming bent.
A need therefore exists for an improved split-bolt which can be quickly, simply and efficiently inserted in and extracted from, e.g., a coil insert, while being durable enough that the wedge member will not become readily bent such as to render the split-bolt inoperative.